Yahoo won't send to .biz account

I have a client with a Yahoo account. Two emails to my .biz address failed to go thru. One with an attachment, one very small just text.
Does Yahoo have an aversion to .biz? Never got a reject notice, or failure message, everything seems to have fallen into the bit bucket!
Same emails went AOK to gmail and bellsouth.net.
Not that it should matter, but both computers are running Win 8.1; Mail was created via IE - Yahoo.mail.
Otherwise, the account seems to be functioning "within normal parameters".
Bob

Just after posting this, my email client received the first message-ONE HOUR AFTER SENDING! ???